An excerpt from "The Brain Makers" by HP Newquist (pg. 196):
Before long, Symbolics officials claimed that Stallman was actually taking the code that they were giving back to the lab, and that he was forwarding it to Greenblatt. Symbolics hackers even monitored Stallman's activities by using a little known feature that enabled networked LISP machines to watch what other LISP machines were doing. In essence, a hacker on LISP machine A could literally watch the screen activities of LISP machine B. After a few of these spying sessions, it became clear to Symbolics that Stallman was forwarding LISP code to LMI.
Several Symbolics executives approached MIT's administration and presented their evidence. Do something about Stallman, Symbolics' executives demanded. In order to keep its relationship with Symbolics on an even keel, MIT warned Stallman to stay away from the various LISP projects, but stopped short of denying him access to the lab's computing facilities. One more infraction, however, and Stallman might never again be allowed to get near an MIT computer.
This was too much for Stallman. Symbolics had not only raped the AI Lab and stolen all of its employees, thus destroying the hacker culture, but now it had tried to stop him from hacking. In a fit of rage, Stallman allegedly sent an electronic mail message out from the AI Lab that said, in effect: I will wrap myself in dynamite and walk into Symbolics' offices, and I will blow the whole company up.
Stallman was fanatical, but this supposed threat was potentially more dangerous than anything else he had ever done. The message caused a brief flurry of excitement and speculation on the part of Symbolics' employees, but ultimately, no one took Stallman's outburst all that seriously. Despite his vehemence, Stallman never did get the dynamite.
Though this incident has been confirmed by several Symbolics executives. Stallman himself has no recollection of it. "I fought Symbolics with all my might for two years, but I didn't do it with threats," he says. "I am sure I never made such a threat to Symbolics. On the other hand, I can't be sure I never said that to anyone. I had some heated arguments with Symbolics employees, and we sometimes lost our tempers. Perhaps this story is based on one such event. I was definitely upset enough about the destruction of the AI lab."